Controlled burst firing mechanism



Nov. 28, 1961 s. D. SILSBY 3,010,370

CONTROLLEDBURST FIRINGMECHANISM Filed April 5, 1961 4 Sheets-Sheet 1 Fig. l-

INVENTOR. 511E111 25 11-5 fishy Nov. 28, 1961 s. D. SILSBY 3,010,370

CONTROLLED BURST FIRING MECHANISM Filed April 5, 1961 4 Sheets-Sheet 2 Fig-EL IN V EN TOR.

Eiunley 1:1- Elflsby Y J64. Raw 9 12 QM? Nov. 28, 1961 s. D. SILSBY 3,

CONTROLLED BURST FIRING MECHANISM Filed April 5, 1961 4 Sheets-Sheet 3 INVENTOR- 51EL111EYD. Elilshy BY 1961 s. D.$|LSBY 3,010,370

CONTROLLED BURST FIRING MECHANISM Filed April 5, 1961 4 Sheets-Sheet 4 United States Patent CONTROLLED BURST FIRING MECHANISM Stanley D. Silshy, Granby, Mass, assignor to the United States of America as represented by the Secretary of the Army Filed Apr. 5, 1961, Ser. No. 101,030

6 Claims. (Cl. 89-129) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to firearms and more particularly to the firing mechanisms therefor.

Firearms which are designed for military use must be adaptable to as many conditions as possible. There are times when the degree of accuracy desired of a shoulder arm is such that the accuracy can be provided only through single file operation. There are other times when conditions require maximum fire power produced continuously at a higher rate.

However, when a firearm which is designed to fire at a high rate is operated in short bursts by manual control of the trigger, there is a considerable waste of ammunition as the number of rounds fired is generally in excess of that required. The general solution of this problem has been to reduce the firing rate of the firearms which, consequently, reduces their efficiency, accuracy and the benefits resulting from a cone of fire produced at a high rate.

It is, therefore, an object of this invention to provide for firearms having a trigger-actuated hammer and a reciprocal bolt, a firing mechanism which may be easily adjusted for continuous automatic fire at the optimum high rate for which it was designed, for single fire, or for bursts of a selected number of rounds each time the trigger is actuated.

It is another object of this invention to provide a firing mechanism having a counter which automatically returns to its normal, initial position upon release of the trigger at the termination of a burst to assure that the subsequent burst will provide the selected number of dis charges.

It is a further object of this invention to provide such a firing mechanism in which the selector which adjusts the firing mechanism for automatic, semiautomatic, or selective burst operation also provides a selective safety device which blocks the actuation of the sear by the trigger.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a longitudinally cross-sectioned side view of the fragmentary portions of a rifle containing the firing and trigger mechanisms and shows the firing mechanism with the hammer seared in the cock position and the trigger mechanism with the trigger in the normal position thereof;

FIG. 2 is a view similar to FIG. 1 but showing the trigger in the fire position and the hammer released to the firing pin striking position;

FIG. 3 is a view similar to FIG. 1 but showing the hammer retracted by the bolt to the overtravel position;

FIG. 4 is a view taken along line 4--4 of FIG. 3;

FIG. 5 is a view talcen along line 5-5 of FIG. 2;

FIG. 6 is a view taken along line 6-6 of FIG. 3;

FIG. 7 is a longitudinally cross-sectioned view of the firing mechanism taken along line 7-7 in FIG. 5 showing the hammer engaged by the secondary sear after the first round of a two-round burst is discharged;

FIG. 8 is a view similar to FIG. 7 but showing the ice relationship of the parts after the fourth discharge of a continuous automatic burst of fire;

FIG. 9 is a view similar to FIG. 7 but showing the relationship of the parts when the selector is adjusted to the safe position to block the release of the sear by the trigger;

FIG. 10 is a fragmentary view of the bottom of firing mechanism housing showing the selector adjusted for firing a two-round burst;

FIG. 11 is an exploded, perspective view of the firing mechanism;

FIG. 12. is a fragmentary, perspective view of the actuator; and

FIG. 13 is an exploded, perspective view of the trigger and the toggle-connector.

Shown in the figures is a rifle 12 provided with a receiver 14 in which a bolt 16 is disposed for longitudinal reciprocation in recoil and counterrecoil strokes responsiye to recoil forces produced by the discharge of a barrel chambered cartridge (not shown). The chambered cartridge is discharged by a firing mechanism 18 which is adapted, as hereinafter described, to fire each time a trigger 20 is actuated, either a single round, a continuous burst, or a burst of two, three, or four rounds as selected.

Trigger 20 is pivotally mounted in a trigger guard 28 fixed to the underside of receiver 14 forwardly of a magazine 22. Trigger 20 includes a fingerpiece 2A4 and an arm 26 disposed relative thereto at an acute angle and is mounted in trigger guard 28 for pivotal displacement between a forward normal position and a rearward fire position by means of a transversely disposed pin 30 which is matingly received by a hole 31 located at the top, front corner of the trigger on the longitudinal center line of arm 26. When trigger 20 is in the normal position (FIG. 1), arm Z6 inclines downwardly and rearwardly respective to pin 30 and, when the trigger is in the fire position (FIG. 2.), the arm extends longitudinally rearward from pin 30. A spring-pressed plunger 34 is mounted in trigger guard 28 so as to press forwardly against fingerpiece 24 for biasing trigger 20 to the normal position.

A trigger bar 36 extends longitudinally within receiver 14 between trigger guard 28 and a housing 38 for firing mechanism '18, which housing is fixed to the underside of receiver .14 rearwardly of magazine22. Trigger bar 36 is disposed in receiver 14 for sliding, longitudinal displacement and is connected at the front end to trigger 20 by means of a toggle-connector 40 which converts the pivotal displacement of the trigger to translational displacement of the trigger bar and permits longitudinal displacement thereof relative to the trigger, when the trigger is in the fire position, wherein arm 26 is in longitudinal alignment with the trigger bar. Toggle-connector 40 includes a connector bar 42 and a telescopic pin device 44 having a cylindrical front pin 46 and a tubular rear pin 48 which receives such front pin for relative axial displacement. A coil spring 50 is operationally disposed between front and rear pins 46 and 48 for biasing such pins apart to relatively extended positions.

The rear ends of connector bar 42 and rear pin 48 are both pivotally mounted on the front end of trigger bar 36 by means of a transversal pin 52 which is received by mating holes in such connector bar and rear pin. The front ends of front pin 46 and connector bar 42 are pivotally mounted onthe rear end of arm 26 by means of a transversal pin 54 which is received by a mating hole in front pin 46 and by :a longitudinal slot 56 in the connector bar 42 to permit longitudinal displacement of trigger bar 36 relative to trigger 20 when the trigger is in the fire position. When trigger 20 is in the fire position wherein arm 26 and trigger bar 36 are longitudinally aligned, 9.

forward displacement of the trigger bar, as permitted by slot 56, telescopes pin device 44 and compresses spring 50. However, the tension of spring 50 is sufficient to hold pin 54 against the front end of slot 56 during actuation of trigger 20 between the normal and fire positions thereof for positive transfer of movement thereof to trigger bar 36.

Mounted in housing '38, as hereinafter described, is a pivotal hammer 58 which is disposed for striking the rear end of a firing pin 60 in bolt '16, a primary sear 62 which cooperates with the hammer for initiating and terminating a burst, a secondary sear 63 for releasably holding the hammer in a cock position until the bolt is in battery position, an actuator 64 disposed for pivotal oscillation by said hammer during overtravel thereof past the cock position, and a rounds counter 66 disposed for pivotal displacement by trigger b-ar 36 against the primary sear 62 when the trigger is pulled to the fire position and for incremental step displacement vertically responsive to oscillation of the actuator.

Hammer 58 includes .a cylindrical sleeve 68 rota-tingly mounted on a shaft 70 transversely disposed through housing 38, a stem 72 extending radially from the sleeve and a head 74 integrally formed on the outer end of the stem for striking firing pin 60. Stem 72 is offset to the right of the center of head 74 so as to clear primary sear 62 and counter 66 when hammer 58 swings between the cock and striking positions thereof. Reference to rightor left-hand positions is always in respect to the side of rifle 12 looking forwardly from the butt thereof. A plug 76 extends to the right of head 74 from the striking surface thereof for contact by secondary sear 63, as hereinafter described, and a stop-arm 78 extends integrally from sleeve 68 diametrically opposite stem 72. Head 74 is disposed for contact by bolt 16, during the recoil strokes thereof, for pivotally displacing hammer 58 from the striking position thereof to an oventravel position past the cock position. A spring device 80 is operationally disposed between stem 72 and a transversal shaft 82 through the rear end of housing 38 for biasing hammer 58 to the striking position. A pad 84 is disposed in housing 38 for contact with head 74 when hammer 58 is in the overtravel position to limit the counterclockwise rotation thereof.

Counter 66 is of elongated configuration and is mounted on a transversal rod 86 in a substantially vertical position. Rod 86 is received by an elongated slot 88 which is closed at both ends and which is vertically formed in counter 66. Whereby, counter 66 is disposed for pivotal displacement around rod 86 and for vertical displacement limited by the length of slot 88. A shaft 90 is pivotally mounted at one end to the top of counter 66 and inclines downwardly and rearwardly therefrom with the opposite end being slidingly received by a mating hole 92 extending through a pad 94 positioned inside housing 38 adjacent the bottom thereof and rearwardly of shaft 70. A compressible coil spring 96 is coiled around shaft 90 with one end abutting pad 94 and the other end abutting a stop 98 at the top end of shaft 90 to preload the spring. Pad 94 is positioned so that the load in spring 96 biases counter 66 pivotally around rod 86 in a clockwise direction until the upper end of the counter contacts the front end of housing 38 and also biases the counter upwardly until the bottom end of slot 88 contacts such rod.

A cam surface 100 extends :angularly downward and rearward from the top, front corner of counter 66 and is disposed so as to be contactable by a rounded end 102 on trigger bar 36 in any position of the counter within the range of the vertical displacement thereof permitted by slot 88. The engagement of rounded end 102 with cam surface 100, when trigger 20 is pulled to the fire position, converts the longitudinal displacement of trigger bar 36 to rotational displacement of counter 66 with the tension of spring 50 of toggle-connector 40 being designed to overpower that of spring 96. The pivotal displacement of counter 66 is transferred, as hereinafter described, to primary sear 62 for actuation thereof from a hammer holding position to a position for release of the hammer.

Primary sear 62 is pivotally mounted on rod 86 on the right side of counter 66 and in the same plane as the olfset portion of hammer head 74. Primary sear 62 includes an arm 104 which extends rearwardly so that the end thereof makes in-line contact with a cooperating planar surface 106 on head 74, when the primary sear is in the holding position, for releasably retaining hammer 58 in the cock position. A downwardly facing lip 108 extends forwardly on primary sear 62 for contact, when the primary sear is in the hammer holding position, with an upwardly facing ledge 110 extending into housing 38 from the front end thereof to limit the clockwise displacement of the primary sear. A leg 112 extends downwardly on primary sear 62 below rod 86 for contact, as hereinafter described, with a step section 114 which is formed on the right side of counter 66 and in the same longitudinal plane as the primary sear so that pivotal displacement of the counter by trigger 20 is transferred to the primary sear for actuation from the hammer holding position. The front side of leg 112 contacts the adjacent section of the front end of housing 38 when primary sear 62 is in the hammer release position. A ball bearing 116 is slidingly received by a mating bore 118 extending forwardly into the front end of housing 38 and such ball bearing is backed by a coil spring 119 so as to be resiliently pressed against the front side of leg 112 for biasing primary sear 62 in a clockwise direction to the hammer holding position.

Secondary sear 63 has a configuration substantially the same as primary sear 62 and is pivotally mounted on rod 86 on the right side of the primary sear in the same vertical plane occupied by lug 76 on hammer 58. Secondary sear 63 includes an arm 120 which is spaced sufficiently to the right of arm 104 on primary sear 62 to provide clearance for the passage of stem 72 therebetween when hammer '58 is displaced between the cock and striking positions thereof. The end of arm 120 is engageable with lug 76 on head 74 for releasably holding hammer 58 in the cock position and the top surface of the arm is disposed for sliding engagement by such lug to prevent displacement of secondary sear 63 to the holding position, after release of the hammer, until the hammer overtravels past the cock position.

A downwardly facing lip 122 on secondary sear 63 contacts ledge 110, similar to primary sear 62, when the secondary sear is in the hammer holding position. A leg 1:24 extends downwardly on secondary sear 63 and is disposed for contact with the front end of housing 38 when the secondary sear is in a hammer release position. A spring-biased, ball bearing 126 is mounted in the front end of housing 38 similar to ball bearing 116 for contacting leg 124 to bias secondary sear 63 to the hammer holding position.

A bell crank lever 128 is pivotally mounted to the front end of housing 38 on a transverse pin 129 so that one arm 130 is received by a longitudinal recess 132 in ledge 110 and is positioned for actuation against lip 122 to pivot secondary sear 63 to the hammer release position. Bell crank lever 128 also includes another arm- 134, which extends upwardly at susbtantially right angles to arm 130 for cont-act by a boss .136 on bolt 16 when adjacent battery position, so that, when the bolt is battery positioned and locked, secondary sear 63 is actuated to the hammer release position.

Step section 114 has a configuration best described as a flight of stairs which ascend upwardly and rearwardly from the bottom of counter 66 and which are disposed for engageable cooperation with leg 1-12 and actuator 64, as hereinafter described, so that counter 66 is displaced downwardly one step each time a round is fired. Step section 114 includes four steps 138 each of which is formed by a forwardly facing riser 140 and a tread 142 disposed substantially at right angles thereto. When counter 66 is in its topmost position, as determined by the contact of the bottom end of slot 88 with rod 86, the bottom one of the risers 140 is in contact with the rear side of leg 112 adjacent the end thereof. Whereby, rotation of counter 66 around rod 86 by trigger 20, when pulled to the fire position, causes rotation of primary sear 62 to the hammer release position to initiate a burst. lActuator 64 is oscillated to pull counter 66 downwardly one step responsive to the discharge of each round, as hereinafter described. Through the bias of ball bearing 116, the end of leg 1.12 is displaceable into contact with successive ones of the treads 142 and the associated riser 140 in back thereof. In order to bring the treads 142 successively into position for contact with the bottom of leg 112, counter 66 is provided with a pivotal component of movement, as it is drawn downwardly, so that the bottom pom-tion thereof is displaced forwardly. This pivotal component of movement is achieved by the contact of rounded end 102 on trigger bar 36 with cam surface 82 on the upper front side of counter 66 and the bias of spring 50 in toggle-connector 40 transferred through trigger bar 36 to counter 66. The rear side of counter 66 is .arcuately formed, as noted at 144, to provide a clearance for sleeve 68 of hammer 58 as the counter is actuated past the sleeve. Provided along the underside of step section 114 are three notches 146 which provide clearances for receiving stop-arm 78 on hammer 58 when the hammer is pivoted to the overtravel position thereof. Each of the notches 146 is provided with a top surface 148 which is contact-able with stop-arm 78 when hammer 58 is in the overtravel position, to prevent the displacement of counter 66 more than one step.

Actuator 64 is pivotally mounted on shaft 82 and extends forwardly beyond primary sear 62 so that a tongue 1'50 extending laterally fro-m the left side of the actuator at the front end thereof is contaotable with successive ones of the steps 138. Tongue 150 includes a planar bottom surface 152 successively contactable with the treads 142 and a planar rear surface 154 contactable with the one of the risers 140 at the back of the tread contacted by such bottom surface. The end of leg 112 is arranged to contact the left half of the treads 142 and bottom surface 152 the right half thereof so that both may be in contact with one of the treads at the same time. A projection 155 extends upwardly from the left portion of the top one of the risers 140 for contact with the rear side of arm 112 to hold primary sear 62 in the holding posi tion when the end of the arm is in contact with the top one of the treads 142.

Provided in actuator 64 is a clearance 156 which receives that portion of sleeve 68 which extends to the right of stem 72 to permit uninterrupted displacement of the actuator. The top of clearance 1'56, noted at 1-58, is arcuately formed concentric with shaft 70 and extending reanwardly from the top of the clearance is a cam slot 160 which is disposed eccentric to the shaft as hereinafter described. A cylindrical cam follower 162 extends from the right side of stem 72 to be received by clearance 156 adjacent top surface 158 thereof. Cam follower 162 travel-s along adjacent top clearance 158 during pivotal displacement of hammer 58 between the cook and striking positions thereof and in cam slot 160 during travel of the hammer between the cock and overtravel positions.

Because clearance top 158 is concentric to shaft 70, actuator 64 is not afie'cted by the pivotal displacement of hammer 58 between the cock and striking positions but cam slot 160 is generated so that, during travel of the hammer from the cock to the overtravel position, the actuator is pivoted downwardly sufficiently to displace tongue "150 a distance equal to the height of a riser 140. When hammer 58 travels between the overtravel and cock positions, the engagement of cam follower 162 with cam slot 1'60 pivotally displaces actuator 64 upwardly.

A selector 1 64 with a stop-arm :166 is slidingly mounted on the bottom of housing 38 for longitudinal displacement with such stop-arm extending upwardly thereinto for contact by the bottom one of the risers 140. Displacement of selector 164 is provided by a knob 168 fixed to a vertically depending axle 169 rotatingly mounted to the bottom of housing 38. Axle 169' is provided with a pin 170 which extends eccentrically therefrom so as to be slidingly received by a slot '172 in selector 1164. Whereby, rotation of knob 168 is converted to translational displacement of selector 164. A springbiased detent 174 is disposed in knob 168 for cooperation with six indentations 176 in the bottom of housing 38 for selectively indexing selector 164 in one of six positions. A recess 178 in the circumference of knob 168 provides a window for visually identifying markings which are provided in the bottom of housing in reference to the six selective positions of selector 164 so that the position to which the selector is actuated by the knob may be identified as best shown in FIG. 9. The reference markings comprise S, l, 2, 3, "4 and A. When recess 178 is in registry with S, which signifies that firing mechanism '18 is made safe against accidental discharge, selector 1 64 is positioned so that stop-arm 166 has contact with bottom riser 140, as best shown in FIG. 8, when the counter 66 is in its initial uppermost position. Whereby, counter 66 is blocked against displacement against primary sear 62 so that trigger 20 cannot actuate the counter to pivot the primary sear for release of hammer 58 until knob 168 is turned from S position.

When knob 168 is turned to where 1 appears in recess 178, firing mechanism 18 is adjusted for semiautomatic fire so that only one round is fired each time trigger 20 is actuated. This is accomplished by selector 164 being positioned so that stop-arm 166 is contacted by bottom riser to block displacement of counter 66 by spring 50 against leg D12 of primary sea-r 62 during clockwise rotation of hammer 58 from the overtravel position thereof after one round is fired. Whereby, primary sear 62 is held by spring-pressed, ball bearing 116 in position for engaging hammer 5-8 during return thereof to the cock position.

When knob 168 is turned to where recess 178 is in registry with reference markings 2, "3 or 4, selector 164 is adjusted to where stop-arm 166 blocks pivotal displacement of counter 66 against primary sear 62, during clockwise rotation of hammer 58 from the overtravel position thereof, after two, three or four rounds, respectively, have been fired in a burst.

To adjust firing mechanism 18 for firing automatically and continuously so long as trigger 20 is pulled-to the fire position, knob :16-8 is turned to where A shows in recess 178. In this position, selector '164 is adjusted to where stop-arm 166 is not contactable by counter 66 to block displacement thereof. Consequently, during the first four discharges of a burst, counter 66 is actuated downwardly four steps to where tongue contacts the top one of the treads 142. Thereafter, oscillation of actuator 64 by hammer 58 cannot displace counter 66 further but the firing will continue so long as trigger 20 is held in the fire position because projection at the top of step section 1 14 is positioned to engageably hold primary sear 62 in the release position.

The downward displacement of counter 66 during its operational function has both a pivotal and a vertical component of movement, as hereinbefore explained, and therefore to compensate for this arcuate movement, the contacting surface of stop-arm 166 is arcuately formed as shown at 180 to assure blocking contact with the counter in each of the selective positions of selector 164.

Operation release position and hammer 5-8 is held in cock position 7 by primary sear 62. If rifle 12 is to be fired in bursts of two rounds each time trigger 20 is pulled, knob 168 is rotated to where 2 shows in recess 178. To initiate a burst, trigger 20 is pulled to the fire position whereby arm 26 is swung upwardly to straighten out toggle-connector 40, relative to the arm and trigger bar 36, and thereby push the trigger bar rearwardly. The rearward displacement of trigger bar 36 causes rounded end 102 thereon to be actuated against cam surface 100 on counter 66 and thereby rotates the top end thereof rearwardly and the bottom portion including step section 114 forwardly around rod 86. Thus, the bottom one of the risers 140 is actuated forwardly against leg 1 12 of primary sear 62 which is pivoted thereby in a counterclockwise direction to the release position. Hammer 58, upon release from primary sea-r 62, swings forwardly under the bias of spring 80 to strike firing pin 60 for discharge of the barrel chambered cartridge (not shown).

Responsive to the forces of the discharge, bolt 16 is energized for reciprocation in recoil and counterrecoil strokes. During the recoil stroke, hammer 58 is engaged by bolt 16 so as to be swung from the striking to the overtravel position. During initial displacement of hammer 58, cam follower 162 thereon travels inside clearance 156 along clearance top 158. When bolt 16 leaves battery position, boss 136 thereon is moved away from contact with arm 134 of bell crank lever 128, thereby permitting secondary sear 63 to be biased by springpressed, ball bearing 126 towards the holding position thereof. Secondary sear, however, is prevented from being displaced fully to the holding position because of the sliding contact of the top surface of arm 120 with lug 76 until hammer 58 reaches cock position.

When hammer 58 reaches cock position, lug 76 is displaced clear of arm 120 freeing secondary sear 63 for actuation to the holding position by spring-pressed, ball bearing 126. Also at this point, cam follower 1 62 enters cam slot 160 of actuator 64 which is pivoted downwardly thereby during the continued travel of the hammer to the overtravel position. The downward displacement of actuator 64 causes tongue 150 to be actuated against the bottom one of the treads 142 which was displaced under the tongue when counter 66 was pivotally displaced by trigger 20. The downward displacement of tongue 150 against the associated tread 142 pulls counter- 66 downwardly one step and thereby actuates carn surface 100 against rounded end 102 of trigger bar 36. The displacement of stop-arm 78 on hammer 58 into the first one of the notches 146, when the hammer goes into overtravel position, prevents counter 66 from being displaced more than one step.

The actuation of cam surface 100 against rounded end 102 forces trigger bar 36 forwardly to telescope toggleconnector 40 and compresses spring 50 with the load thereof being taken linearly by arm 26 because of the longitudinal alignment of trigger bar 36, the toggle-connector and the arm when trigger 20 is in the fire position. Therefore, because the forward application of force is taken by pin 30, the load in spring 50 is applied trearwardly against counter 66 to force the bottom one of the risers 140 forwardly against leg 112 which is blocked against forward movement by the contact thereof with the front end of housing 38. When hammer 58 is adjacent overtravel position, counter 66 is displaced downwardly by actuator 64 sufficiently so that the bottom one of the risers 140 is lowered clear of leg 112. This permits counter 66 ,to be rotated by spring 50 to where the second one of the risers '140 contacts rear surface 154 of tongue 150. The forward displacement of step section 114 also moves the second one of the risers 140 into contact with leg 112 to positively position the end thereof in position for contact with the bottom one of the treads 142.

When bolt 16 sequentially returns toward battery position and hammer 58 is freed thereby for clockwise rotation by spring 96 from the overtravel position, cam follower 162 moves forwardly in cam slot 160 to pivot actuator 64 upwardly. This causes tongue 150 to be raised upwardly sliding along the second one of the risers with counter 66 being held against upward displacement through the contact of the end of leg 112 with the bottom one of the treads 142. When hammer 58 is adjacent cock position, tongue is positioned clear of the engaged riser 140 freeing counter 66 for counterclockwise rotation by spring 50. The resulting forward displacement of step section 114 causes the second one of the risers 140 to be actuated against leg 112 and thereby pivot primary sear 62 to the release position thereof. However, secondary sear 63 remains in the holding position thereof, through the bias of ball bearing 126, to hold hammer 58 in the cock position.

When bolt 16 reaches battery position and is locked by means not shown nor a part of this invention, boss 136 in the bolt contacts arm 134 of bell crank lever 128. This pivots bell crank lever 128 to raise arm 130 thereof against lip 122 of secondary sear 63 for actuation thereof to the release position, whereby hammer 58 is freed to strike firing pin 60 for discharge of another barrel chambered cartridge (not shown).

Responsive to the forces generated by the discharge, the above recited sequences of operation are repeated to the point where hammer 58 swings forwardly from the overtravel position. With selector 164 indexed in 2 position, stop-arm 166 is located so as to be s-lidingly contacted by the bottom end of counter 66 when released from tongue 150 at the end of the first firing cycle. Consequently, counter 66 is blocked by stop-arm 16 6 against displacement after release from tongue 150 following the second discharge, whereby primary sear 62 remains in the holding position so that arm 104 thereof holds hammer 58 in cock position and terminates the burst.

When trigger 20 is released to the normal position after termination of the two-round burst, trigger bar 36 is displaced forwardly to relieve the pressure of rounded end 102 against cam surface 100. This permits clockwise displacement of counter 66 by spring 96 and thereby moves the second one of the treads 142 clear of the end of leg 112. Thus, counter 66 is freed for vertical displacement by spring 96 to its initial upper position so as to be automatically reset and ready for counting another burst of two rounds when trigger 20 i pulled to the fire position. Thereby, with this automatic resetting feature of firing mechanism 18, it is obvious that, even if a burst is interrupted by release of trigger 20 before the selected number of rounds are fired, the subsequent lburst initiated by the trigger will have the number of discharges for which selector 164 is adjusted. Moreover, as explained hereinbefore, when selector 164 is adjusted by knob 168 to the S position, firing mechanism 18 is prevented from firing and so rifle 12 is made safe against accidental discharge by trigger 20. In 1 position, rifle =12 is adjusted for semiautomatic fire. In 2, 3 and 4 positions, firing mechanism 18 is adjusted for firing bursts of two, three and four rounds, respectively. When knob 168 is turned to A position, rifle 12 will fire automatically as long as trigger 20 is held in the fire position.

From the foregoing, it is clearly apparent that there is provided herein a firing mechanism which is adjustable for firing a selected number of rounds each time the trigger is pulled and which is adjustable to provide semiautomatic and automatic operation as well as provide a safety for preventing accidental discharge by the trigger, which firing mechanism is simple but rugged in construction, is easy to manufacture and is positive in its functions.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

I claim:

1. In a firearm, a firing mechanism including a hammer pivotal between a firing pin striking position and an overtravel position, a primary sear pivotally disposed for releasably holding said hammer in a cock position between the striking and overtravel positions thereof, a trigger bar connected to a trigger for actuation thereby, a counter operationally disposed between said sear and said trigger bar for converting a force applied thereby to said counter to pivotal displacement of said primary sear to a position for release of said hammer, means for mounting said counter for combined pivotal and vertical displacement relative to said primary sear, an actuator disposed for cyclic oscillation by said hammer during displacement thereof between the cock and overtravel positions, and means for converting cyclic oscillation of said actuator to step displacement of said counter and sequential actuation thereby of said primary sear between the positions for holding and for releasing said hammer.

2. The firing mechanism as defined in claim 1 wherein said primary sear is pivotally mounted on a rod transversely disposed therethrough, and said means for mounting said counter for combined pivotal and vertical displacement includes a vertical slot disposed in said counter for receiving said rod.

3. The firing mechanism as defined in claim 1 and including a cam follower extending from said hammer and a cam slot formed in said actuator for slidingly receiving said cam follower during displacement of said hammer between the cock and overtravel positions thereof, said cam slot being formed to transfer pivotal displacement of said hammer to said actuator for cyclic oscillation thereof.

4. The firing mechanism as defined in claim 1 wherein said hammer includes a sleeve rotatingly mounted on a transverse shaft, a stem extending radially from said sleeve, a cylindrical cam follower extending laterally from said stem, a head and a stop-arm disposed for engagement with said counter for limiting the vertical displacement thereof by said actuator, and wherein said actuator is pivotally mounted at one end on a transverse shaft and is provided at the opposite end with a clearance for receiving said sleeve and said cam follower, and an arcuate cam slot extending from said clearance, said cam slot being disposed for receiving said cam follower during displacement of said hammer between the cock and overtravel positions thereof and being generated for transferring pivotal displacement of said hammer to said actuator.

5. The firing mechanism as defined in claim 1 wherein said counter is provided with a vertical slot for receiving a rod to mount said counter for combined pivotal and vertical displacement, and a spring is disposed between said counter and a pad in a housing for the firing mechanism so as to bias said counter for pivotal displacement away from said scar and upwardly relative thereto.

6. The firing mechanism as defined in claim 1 wherein said counter is of elongated configuration and is disposed in a substantially vertical position, said means for mounting said counter comprises a slot formed in said counter intermediate top and bottom ends thereof and a rod disposed transversely through said slot, and said trigger bar is actuatable against said counter adjacent the top end thereof for displacing the bottom end against a leg of said primary sear for displacement thereof to a position for release of said hammer, and including a spring disposed between the top end of said counter and a pad in a housing for the trigger mechanism for biasing said counter upwardly on said rod and displacing the bottom end of said counter pivotally away from engagement with the leg of said sear.

7. The firing mechanism as defined in claim 1 wherein said counter is of elongated configuration and is disposed in a substantially vertical position wherein said means for mounting said counter comprises a slot formed in said counter intermediate top and bottom ends thereof and a rod disposed transversely through said slot, wherein said trigger bar is actuatable against said counter above said slot for displacing the portion of said counter below said rod against said primary sear, and wherein said means for converting cyclic oscillation of said actuator to step displacement of said counter and sequential actuation of said primary sear includes a step section provided with a plurality of steps formed on one side of said counter below said slot so that said steps are successively engageable by said actuator during cyclic oscillation thereof for vertical displacement of said counter, and means for resiliently biasing said trigger bar against said counter for displacing said step section into position for engagement of successive ones of said steps by said actuator during sequential oscillation thereof and for pressing said step section against said primary sear for actuation thereof to the position for release of said hammer.

8. The firing mechanism as defined in claim 1 wherein said counter is intermediately mounted between the top and bottom ends on a transverse rod for combined vertical and pivotal displacement, said trigger bar is disposed for actuation against said counter adjacent the top end thereof so as to displace the bottom end pivotally against said primary sear for actuation thereof to the release position, and said means for converting cyclic oscillation of said actuator to step displacement of said counter and sequential actuation thereby of said primary sear includes a step section provided with a plurality of steps formed on one side of said counter at the lower portion thereof so as to ascend from the bottom end thereof and so as to be actuatable by said trigger bar against said primary sear for displacement thereof to the release position, a tongue extending from said actuator for actuation against one of said steps when disposed in registry therewith to displace said counter vertically, spring means disposed between said trigger and said trigger bar for pressing said trigger bar against said counter to pivotally bias said step section towards said tongue for registering successive ones of said steps therewith, and a leg on said primary sear disposed for engagement with successive ones of said steps so as to be actuated thereby to the release position when said step section is pivotally displaced by said spring means for successively moving said steps in registry with said tongue.

9. The firing mechanism as defined in claim 1 wherein said trigger is mounted on a transverse pin for pivotal displacement between a normal and a fire position and is provided with an arm which when said trigger is in the fire position is linearly disposed relative to said trigger bar and which when said trigger is in the normal position is angularly disposed relative thereto, and wherein a telescopic toggle-connector connects said arm with said trigger bar to convert pivotal displacement of said trigger between the normal and fire positions thereof to translational displacement of said trigger bar and when said trigger is held in the fire position permits translational displacement of said trigger bar relative thereto.

10. The firing mechanism as defined in claim 1 and including selector means adjustingly disposed in a housing for the tiring mechanism so as to be clear of contact by said counter for selectively blocking pivotal displacement of said counter against said primary sear by said trigger and after actuation of the firing mechanism a selected number of cycles.

11. The firing mechanism as defined in claim 1 and including a secondary sear pivotally disposed for releasably stopping said hammer in the cock position during displacement thereof from the oventravel position, and a pivotal bell crank lever having a first arm disposed for actuation against said secondary sear for displacement thereof to a position for release of said hammer and a second arm disposed for contact by a reciprocal bolt in the firearm when the bolt is adjacent a battery position for pivoting said first arm against said secondary sear for release of said hammer.

12. In a firearm having a receiver provided with a bolt disposed for reciprocation between a battery and a recoil position and a cartridge magazine mounted to the receiver, a trigger guard mounted on the receiver forwardly of the magazine, a trigger pivotally disposed in said trigger guard on a transverse pin for displacement between a normal and a fire position, a trigger bar extending rearwardly from said trigger into a housing mounted on the receiver rearwardly of the magazine, a telescopic toggleconnector disposed between said trigger and said trigger bar for converting pivotal displacement of said trigger to translational displacement of said trigger bar and providing for longitudinal displacement thereof relative to said trigger when in the fire position, a spring disposed for operational cooperation with said toggle-connector so as to be loaded when said trigger bar is displaced towards said trigger, said housing supporting a hammer pivotally mounted on a transversal shaft for pivotal displacement between a firing pin striking position and an overtravel position and for engagement by the bolt during movement thereof to the recoil position so as to be actuated thereby to the overtravel position, a primary sear pivotally mounted on a transversal rod for releasably holding said hammer in a cock position between the striking and overtravel positions, a spring-pressed ball bearing disposed between said primary sear and the front end of said housing for biasing said primary sear to a position for releasably holding said hammer in the cock position, an elongated counter mounted on said rod so as to be vertically disposed and so as to be contacted at the top by the rear end of said trigger bar, said counter being provided with a vertical slot between the top and bottom ends thereof to receive said rod and provide for combined vertical and pivotal movement relative thereto, said slot being closed at both ends to limit the upper and lower displacement of said counter, an actuator disposed for pivotal oscillation in downward and upward strokes by said hammer during displacement thereof between the cock and overtravel positions, means for converting cyclic oscillation of said actuator to downward step displacement of said counter and the step displacement of said counter to sequential displacement of said primary sear to a position for release of said hammer, and selector means slidingly disposed in said housing for selectively blocking pivotal displacement of said counter after being displaced a selected number of steps.

13. The combination as recited in claim 12 and including a stop arm disposed on said hammer for engagement With cooperating notches in said counter to prevent displacement thereof more than one step for each cyclic displacement of said hammer.

14. The combination as defined in claim 12 wherein said means for converting cyclic oscillation of said actuator to downward step displacement of said counter and the step displacement of said counter to sequential displacement of said primary sear includes on said counter a cam surface inclining downwardly and rearwardly from the top end thereof and a rounded end on said trigger bar disposed for sliding contact with said cam surface 12 whereby downward step displacement of said counter displaces said trgger bar towards said trigger to load said spring disposed between said trigger and trigger bar and thereby bias the bottom end of said counter against a leg on said primary sear for pivotal displacement thereof to a position for release of said hammer.

15. The combination as defined in claim 12 wherein said means for converting cyclic oscillation of said actuator to downward displacement of said counter and the step displacement of said counter to sequential displacement of said primary sear includes a step section formed on one side of said counter for operational cooperation with said leg of said primary sear, said step section including a plurality of steps ascending upwardly and rearwardly from the bottom end of said counter, each of said steps including a riser contactable with the rear side of said leg and a tread contactable with the end thereof, said riser of the bottom one of said steps being disposed for contact with said leg when said counter is in the upper position thereof so that the pivotal displacement of said counter is transferable to said primary sear for actuation thereby to the release position, and a tongue extending laterally from said actuator, said tongue being provided with a bottom surface engageable with successive ones of said treads for transferring the downward strokes of said actuator to said counter for downward displacement thereof and with a rear surface disposed for contact with said riser extending upwardly from said tread engaged by said bottom surface, said rear surface being disposed for blocking pivotal displacement of said counter by said spring through said trigger bar during upward strokes of said actuator until said hammer is adjacent cock position during displacement from the overtravel position and for releasing said counter for actuation thereof through the pressure of said spring against said leg of said primary sear for displacement thereof to the release position before said hammer reaches the cock position.

16. The combination as recited in claim 12 wherein said selector means includes a selector slidingly disposed in the bottom of said housing, said selector being provided with a stop-arm extending integrally upward therefrom so as to be positionable for blocking displacement of the bottom end of said counter so as to prevent displacement of said primary sear thereby to the release position, a knob rotatingly mounted on a vertically disposed shaft fixed to the bottom of said housing, a pin extending from said selector for sliding engagement with a slot in said knob for converting rotation thereof to translational displacement of said selector, and detent means disposed between said knob and the bottom of said housing for selectively indexing said stop-arm on said selector in a position for blocking displacement of said counter initially by said trigger, in a plurality of positions for blocking displacement of said counter after displacement thereof a selective number of steps and in a position to be clear of contact by said counter during step displacement thereof whereby actuation of said primary sear to the holding position is effected by release of said trigger.

No references cited. 

